Pump



March 2 1943.

F. -YC. WOELFER, JR

PUMP

3 VSheets-Sheet 1 Filed March 9, 1940 IVENTOR.

Mdwdavz ATTORNEB March 2 1943. F. c. woELFER, JR

PUMP

Filed March 9, 1940 3 Sheets-Sheet 2 -Ill-M- March 2 1943. F. c. woELFER, JR 2,312,857

PUMP

Filed March 9, 1940 3 Sheets-Sheet 5 A I is Patented` Mar.V 2, 1943 PUMP Frank C. Woelfer, Jr., Cincinnati, Ohio, assigner to The Cincinnati Bail Crank Company, Cincinnati, Ohio, a corporation ot Ohio Application March 9, 1940, serial No. 323,195

iol. s-.5)

8 Claims.

This invention relates to pumping apparatus primarily used for pumping grease or the like from -a drum and delivering the same to a point of use under pressure. More particularly, the invention is directed to pumping apparatus of that type adapted to be mounted on the top of a grease container and including a tube depending into the container to a point adjacent the bottom thereof. The invention relates aswell to a pumping mechanism including an improved pneumatic motor. These so called barrel pumps have been designed to lift the grease from the drum to a high pressure pump contained in the same unit which delivers the grease .under high pressure for supplying the fittings of a motor car.

It has been an object of the present inventor to provide an improved pumping mechanism for lifting the grease from the bottom of a container to a high pressure unit and from this point de. livering the grease under high pressure to the point of use. 'I'he improved mechanism, although driven by the same power unit will not stall due to oversupply of grease to the high pressure pump. It will be appreciated that it is impossible to deliver a fixed amount of grease upon each normal stroke of the lifting or low pressure pump, and that in time the high pressure pump will be oversupplied or undersupplied. Ii undersupplied, the pump is ineilcient and wasteful and if over-l supplied, the operativeness of the mechanism is seriously a'ected for it will stall. Realizing that the output of the lift pump cannot be uniform.

the present inventor has provided means for' creating a slight reserve supply of grease in the chamber adjacent the high pressure punip and at the same time means for preventing too much accumulation. Since the space in which-the low pressure pump is mounted is limited, the present inventor has provided that this last named means may also function as the intake means for the low pressure pump. In the disclosed embodiment means employed for this purpose is constituted by a valve which has a double function either opening for intake purposes for the low pressure pump or opening for bypassing purposes in the event of an oversupply of grease to the high pressure pump.

It has been a further object of the inventor to provide an extremely compact assembly or relationship of the low pressure pump, the high pressure pump and, the power means which drives the pistons of these pumps as a unit.

It has been a further object of the inventor to provide an improved air motor for supplying the power for operating the pumps.

It has been a further object to provide an improved means for mounting the pump mechanism relative to the original container whereby the pump may be quickly and easily placed in position where its low pressure pump is submerged in the grease in the original container. -v

The mechanism including thv.` valved piston device is disclosed and claimed in a co-fiendingv divisional application Serialv No. 442,923, illed May 14, 1942, entitled Pumps, which application was divided from this application,

Other objects and certain advantages will be more fully apparent from a description of 'the drawings in which:`

' Figure 1 is a perspective view of a. pumping mechanism incorporated in a cabinet with its lower pressure pump submerged in the greasein an original container. Figure. 2 is a perspective view showing the pumping unit mounted on the top of a shorter type of grease bucket and illustrating a cooperating base arrangement.

Figure 3 is a sectional view taken vertically through the center of the apparatus showing thedetails thereof, with the pumping mechanism in A' position to start upward in the. grease delivery stroke.

Figure 4 is a fragmentary sectional view of the lower end of the tube containing the low presl sure pump showing the pump piston descending l with the valve thereof in intake `or openposition. Figure 5 is a view taken similar to Figure-4 showing the low pressurepump piston moving upwardly in the delivery stroke. 4

Figure 6 is a sectional view taken on line 8 8 of Figure 3, showing more of the details'of the air motor.

Figure 'I is a sectional view taken on line Ig- 1,

Figure 11 is a diagrammatic view taken sim-- ilar to Figure 10, showing the air motor moving on the rod in the downward stroke with the air below it being exhausted through the valve.

' Referring now to Figure 1 of the drawings, the pump assembly is shown in working position above a grease drum I which is housed in a cabinet 2. The cabinet includes a hinged door at its side and a base which is provided with wheels to facilitate movement of the unit. An air intake conduit 3 supplies air under pressure to the pump assembly while a high pressure grease hose 4, leading from the pump to a grease discharge nozzle 5, provides a controlled means for dispensing the grease. A pair of brackets 6, xed to the wall of the cabinet 2, support the pump assembly so that its intake, which is a. cylinder 1, depends from the head of the pump into the grease drum.

In Figure 2, the pump assembly is shown as a modiiied form in which it is being utilized to pump from a small bucket-type grease container. In this instance a housing 8 is provided for the head of the pump. A plurality of springs 9 cooperate with a ring cover I0, iixed to the pump head, above the grease bucket and a ring base Illa below the bucketl to hold the-assembly rmly in place. In this instance, the intake cylinder 1 is shortened. f

Generally speakin the pump assembly comprises an air motor II, a low pressure large volume pump I2, and a high pressure small volume pump I3. The low pressure pump I2 is disposed below the air motor and sucks grease from the drum and delivers it through a bypass to the high pressure plunger above the air motor. The air motor and pump plungers are in alignment and interconnected so that they reciprocate together.

The low pressure pump I2 operates in the intake cylinder 1. The upper end of cylinder 1 is threaded as at I to be secured to and depend from the air pump casing, shown generally at I5, which houses the air motor II. The lower end of cylinderv 1- is internally threaded to receive an intake cap I1. An aperture I8 in the bottom of the cap I1 provides an intake opening. A bridge I9, spanning the aperture I8, spaces the intake cap from the bottom of the grease drum so that the aperture I8 cannot become closed.

At its upper or inner side, the aperture I8 provides a seat for a check valve 20. Valve is generally disc-shaped having its under, peripheral edge beveled to insure a proper seal when seated. A plurality of guiding fingers 2I extend outwardly and upwardly from the upper face oi the check valve 20 parallel to and in slidable contact with the inner face of the intake cap so that the valve remains centered with respect to the port I8. -A set screw 22, extending through the wall of the cap I1, limits the upward movement of the check valve. v

The pump I2 is connected to the air motor through a connecting rod 23 (Figure 3). The piston 24 of the, pump I2 is slidably supported 23 between two coil springs. A counterturned section 21 oi' the rod 23 provides a shoulder 28 which is engaged by the upper end of the spring 25., The lower end of the springv is engaged by the top of the piston* 24.

The piston 24 comprises a head 29 which is slidably engaged around the counterturned sec- 'Ihe headI is similar to an.

tion 21 of the rod 23. inverted thimble in that an internal counterbore provides a chamber 30. A plurality of discharge passages 3| is bored through the head to open the chamber 30 to the upper side of the piston. 7

the chamber 30. Its outside diameter is smaller' than the inside diameter of the tubular nipple 33, so that a passage 39 exists between the two.

The sleeve 38 rests upon the head of a valve retainer sleeve 4I. When the piston is at rest, as v shown in Figure 3, the sleeve 38 has its upper end spaced slightly from the top of the chamber 30. The A valve retainer sleeve 4I is engaged around a counterturned portion 42 of the rod 23 and its head abutsthe shoulder which is provided by the counterturned portion.

A valve 43 is urged upwardly against the collar by the action of the spring 25 disposed around the bushing 4I under compression between the valve and a washer 44 which is held in place by a nut 45 threaded on the end of the rod 23. The nut'also holds the bushing 4I tightly against the shoulder of the piston rod. The downwardly extended rim or edge of the tubular nipple 33 constitues a seat which is engaged by the spring urged valve 43.

The head of the pump assembly comprises: a

' cylinder block 45 which has a. bypassage 41 and a cylinder bore 48 in which a piston 49 of the air motor I I reciprocates; a casing 50 which includes the high pressure pump I3; and a head 5I which constitutes a guide vfor the piston 49.

The connecting rod 23 extends upwardly lfrom the pump I2 coaxially with the cyilnder 1, and enters the air motor cylinder 48 through a packing gland 52. The upper end of the rod23 is threaded into a nut 53 which in turn is threaded into the lower face ofy the piston 49 of the air motor. The nut 53 has a radial ange 55 which engages a double cup gasket 56 and secures it between the ange piston 49. A metal ring 51 is interposed between the radial flanges of the two cups to stiffen the gasket 58.

A counterturned shoulder 51 in the upper end of the cylinder 48 seats a cup packing gland 58. The head 5I includes a Bange 60 at its lower end which is bolted to the flange 58 of the cylinder block. and holds the packing gland in place. The packing gland 59 provides a seal around the piston 49. The gasket 5B and packing gland 53 provide two chambers in the cylinder bore.

One pressure chamber 52, below the gasket 55,v

v has an effective areaequal to that of the cylin-g der bore minus the crosssection of the rod 23. The other pressure chamber 53, above the piston, has an effective area equal to that of the cylinder bore minus the area of the piston.'

The chamber 52, below the piston 49, has an inlet and exhaust which is controlled by a valve means (disclosed at a later point in the specifica.-l

, tion), while chamber 63, above the piston. ring,

is under constant air pressure.

The downstroke of the piston 49 results due to the fact that the pressure is relieved below the piston and the normal head of pressure above the `piston forces it down. Although the air pressures are the same on both sides, the upstroke 25 or power movement occurs due to the larger and the lower face of the area of contact on the bottom of the piston. Moreover.l the air acting on this larger area produces the high pressure. The downstroke is a low pressure loading stroke.

The head mounted on the top of the cylinder block, has an internal bore 65 into which the piston of the air motor extends when it is moved upwardly on its power stroke. The lower end of the casing 50 for the high pressure cylinder 61 depends into the internal bore 65. The pistbn 49 is tubular as at 68 except for its lower end so as to clear the casing.

The upper portion of casing 50 is iitted into a central bore in the top of the -head 5|. A counterturned portion of bore -10 provides 'a shoulder 12 which abuts a shoulder' 13 on the casing to secure it against upward displacement. The upper end of the casing is threaded internally as at 14 to engage threads on the lower end of th'e grease supply head 1 I A hexagonal flange 15, just above the threads on the head 1|, engages the top of the head 5| so that as the head 1| is threaded into the housing the shoulder 13 on the housing is drawn up against the shoulder 12 in the bore 10, thus xing the casing 50 in place.

vThe outer wall of the cylinder 61, near its upper end, has a counterturned section which provides a shoulder 11. The cylinder is held in place by the nuts 18 of a packing gland A19, at its lower sliding in a vertical bore in the cylinder block 410.

The midsection of the rod 99 is accessible from the outside oi the cylinder block through an opening |0l. The bifurcated end- |02 of a toggle |03 extends into the opening |0| to engage a counterturned section |04 of the rod 99. The counterturned section is of substantially greater length than the swing of the toggle |03 to provide a. certain amount of clearance. The toggle is actuated at the end of each stroke of the piston 49.

A valve support |05 is bolted to the cylinder block 46. A gasket |01 is interposed'between the valve support and the cylinder block. An opening |06 is provided in the base |05'to correspond to the opening |0I. The toggle |03 is supported by a pin |08 which is set in a pair of ears |09 extending outwardly from the base |05, one on either side of the opening |06. The toggle 03 consists of two upright arms joined at their bases. Above and centered, with respect to the pivot point provided by pin |08, another pin ||2 vprovides a rocking support for a collar ||3 on the lower-end of a end which nut is threaded into the casing,50.

When the nut 18 is tightened, the shoulder 11 on cylinder 61 is forced against a shoulder 80, which is on the inside of the bore in the casing 50.

The high pressure plunger I3 extends axially horizontally through the member 82 below the valve. The upper portion of the valve memberis tubular and extends partially up into the bore of pin ||4. The pin ||4wextends upwardly through the middle of a contact wedge H5. The Wedge is urged upwardly against a pair of fingers ||1 by a spring ||'6. The fingers extend from the base 05 on both sides of the pin /I 4. This arrangement provides a snap action toggle.

The outer end H9 of the ltobble |03 is bifurcated and straddlesa counterturned section ||9 of a. valve plunger |20. Section I9 is only slightly the grease supply head 1|. A shoulder 81 on the.

valve member engages the lower edge of the head 1| and is forced downwardly against a shoulder 89 provided by the counterbore 8|. intake ports 90 are provided around the midsection of the valve member. The counterbore 8| is larger than the valve member so that a chamber 9| is provided around the intake ports 90. The grease delivery to the high pressure piston is through a pipe 92 from the bypass chamber 41 in the cylinder block. Pipe 92 is threaded into the casing 50 in a line with the plurality of intake ports A90. A port 93 in the casing 50 between the pipe `92 and the ports 90, connect the two.

As stated above, inlet and exhaust valve means are provided as a control for the air pressure in the cylinder bore beneath the piston 49. The valve means is actuated by a yoke '95 which extends outwardly from a ring 96 which is bolted to the top of the piston 49. The yoke extends through a slot 91 in the wall of the head 5| and A plurality of engages a groove 98 at the upper end o1 a vertiless in length than the complete swing of the tctggles |03, so that the shoulders at the ends of the section 9 are hit sharply by the outer end of the toggle |03, when it rocks.

As shown in Figure 7, the valve plunger |20 open a. Icentral chamber |24 in the head to the atmosphere. The head is threaded into the top of the valve chamber which extends from the base of the valve support |05.

A ledge |25 in a bore |26 inside of the valve chamber provides a valve seat |21. Afvalve |28 is constituted by a flange at the upper end of a sleeve |29 engaged around acounterturned section of the plunger |20 in the bore |216. The inner end of the head |22 includes a rim which constitutes another seat |30 for the valve opposite to the seat |21. The movement of the valve is preferably only about 1% of an inch sol that the change over from one seat to another takes a minimum of time. The lower face of the Valve |28 is beveled to close more tightly on the seat |217. The upper face of the valve |28 supports a packing ring to provide a seal when the valve is closed against the seat |30. Y

The sleeve |29, which has the valve |29 at its upper end. is iixed to the plunger |20 between a @shoulder |3|, provided at its upper end by the counterturned section, and a cup piston ring assembly |32 which is held in place by a washer |33and a nut |34. The nut is threaded on the lower end of the plunger |20..

The'air intake conduit 3 which supplies the air pressure to the motor is connected at .two points to the motor. one une |35 extends into the cylinder of the air motor above the 'cup gasket 56 and is always open. 'I'he other line |36 enters the bore 26 below the valve seat. |21 and is alternately closed from and opened into a port |31 extending to the cylinder of the air motor below the cup gasket ring 56.

Referring to the diagrammatic view, Figure l0, when the plunger |20 is up at the end of the downward movement of the air motor piston, the air comes in through the line |36 past the valve seat |21 and through the port |31 to the chamber 62 below cup piston ring 56. As the piston 49 is moved upwardly, the air above the `gasket is forced back through the bore |35 into the conduit 3. When the plunger |20 is down (Figure 11), the air supply to chamber 62 is closed at the valve seat |21 and chamber 62 is opened to the atmosphere past the seat |30. Allowing the air pressure in the chamber 63, above the cup piston ring 56 to eiIect the return of the piston 49.

When the piston of the air motor moves upwardly, the low pressure grease pump I2 forces grease up through the cylinder 1 through the bypass and port 93 and through the ports 90 into the head. At the same time, the high pressure plunger is moving upwardly, and since the grease above it in the bore of the cylinder l61 is under greater pressure than the grease in the head, the ball check valve 83 remainsI closed. The grease under high pressure cylinder 61 into a bore |39 in the casing wall which is below the check valve and above the upper extremity of the plungers stroke. A nipple |40, threaded into the bore |39 through the wall of head comprises the outlet ior the grease.

On the down stroke of the piston, the check valve 83 opens and grease is` forced by the air above it in the head and by suction, past the valve 93 into the high pressure cylinder bore. At this time, the low pressure pump moves downwardly, opening as it moves (Figure 4) to allow grease to pass through it.

The nipple |40 extends from the head 5| and is engaged by a T |42 at its outer end. A bleeder valve assembly |43 is threaded into the end of the T |42 opposite the nipple I 40. The bleeder comprises a tube |44 having a valve seat which seats a valve |45 xed on a stem |46. The section of plunger outwardly from the valve |45 is square and has threads at its four corners ior engagement with internal threads in the tube at this point. A pin |41 is fixed in the outer end is forced from the bore of of stem |46 to facilitate turning. When the collar |45 is unseatedby unscrewing the stem, a passage is opened past the fiat sides of the square end of the stem. This is provided so that any air that is in the system when the unit is set up can be released easily at this point.

The inner end of the stem beyond the valve |45 is cone shaped to fit into a concavity in the square base |48 of a seat for a spring |49. The coil spring |49 extends to the other side of the T |42 and urges a ball check valve against a seat |50 in the inner end of the nipple |40. The other arm |5| of the T |42 is counterbored to provide a seat |52 which seats a ball check |53. Ball check valve |53 is urged against its seat by a spring |54. The other en d of spring |54 is engaged by the inner end of a threaded section |55 of a swivel coupling |56. Beyond the coupling.

|56 an elbow fitting |56 has the high pressure grease hose 4 connected to it,

This pump 'is' fastened or disposed with respect to the original container in a number of ways. In Figure 3, a. plate |60 is provided providing a flange |6| around its outer edge adapted to overhang the flange of the opening in the top of a drum of lubricant or adapted to overhang the edge of the drum. This cover plate carries lugs i6?! providing inclined bores in which hooks |63 are slidably mounted, The hook portions are disposed around the flange within clearances |64 and are adapted to engage the side of the flange of the drum opening or the edge of the drum. The shanks or the hook bolts extend through the bores of the are screwed thereon bearing against the lugs for drawing the hooks into position. A sleeve |66 is disposed coaxially with the pump and includes a horizontal flange |61 boltedto the cover. The sleeve nts about the circular lower end of the air pump casing |63.

In Figure 1 the pump unit is mounted on a ledge |69 within the cabinet 2 and depends `into the drum generally shown at |10. In Figure 2, the base |0a serves as a support for the short type grease bucket |1|. The springs 9 are disposed under tension between hooks on the base and cooperating hooking means |12 disposed on the cover plate |0 fixed to the casing or the housing 6 of the pump.

Description of operation In operating the pump, it is mounted in any one of the ways shown so as to disclose its tube lair intake conduit 3 and enters the pressure chambers 62-63 in the pump cylinder. This assumes that the valve for the air motor is in the position shown in Figure 10. The air is at the same pressure in both of the chambers. It forces the pump piston 49 upwardly vdue to the diierence between the area of piston exposed in the lower chamber 62 and that exposed in the upper chamber 63. Therefore, the air, in chamber 63 is never lost.

When the piston 49 reaches stroke. the valve is tripped through its mechanism and the lower chamber 62 is then open to the atmosphereas shown in Figure 1l. As the air4 motor piston moves up, the piston of the low pressure pump |2. is drawn up in the tube 1 and grease is lifted to the chamber 1| above the high pressure cylinder 61. As the air motor piston moves up, it also moves the piston of the high pressure pump I3. The high pressure piston causes the valve 03 to close in the high pressure cylinder and the grease is forced out through the line 4 past the check valves therein. In other words, as the grease is being lifted under low pressure for supply purposes for the high pressure pump, the high pressure pump is delivering a high pressure charge through the conduit 4.

In the event that there is too much grease in the tube and the pressure above the high pressure cylinder becomes too great, the resistance to the upstroke of the piston will unseat the valve 43. This occurs when the pressure in the grease is greater than the force of the spring 26 which holds the valve 43 in seated position. The result is then that the grease by-passes through the .piston and the rest of the stroke is lost motion.

lugs and wing nuts |65 then disthe end of its upthe tube above it. As the high pressure piston descends, the vacuum created by the retraction of the high pressure piston draws a supply ot grease into the high pressure cylinder. The head 1| is constantly lled with grease and this accumulated supply column of grease is always available just over the high pressure cylinder. Each time the high pressure pistonv delivers a charge of grease under high pressure,V thelow pressure system lifts a supply.

It is impossible to provide a constant supply on each ,stroke and the volume of grease in the supply chamber varies. In this arrangement, a safety arrangement is provided. Excessive amounts are by-passed and stalling (such as would occur if the grease becomes too tightly packed in the supply chamber) is prevented. 'Ihe same valve which permits iilling of the tube above the piston brings about this by-passage of oversupply.

The chamber provided in the head H over the high pressure cylinder provides a space in which the grease may accumulate. This chamber is referred to as an accumulating or charging chamber since it is just above the high pressure chamber. The moment the high pressure piston starts down, the grease moves into the high pressure cylinder, not only because of expansive pressure in the grease but because of the suction created by the movement of the high pressure piston. Thus it is provided that the is immediately completely lled with grease and the discharge stroke is entirely e'ective;

It will be noted that there isvery little agitation oi the grease. This, of course, is advantageous since "churning or undue working of the grease back and forth in the pump ,tends to break through the body of the grease. As the low pressure piston moves down grease ilows through it. As it moves up, the grease is elevated. If there is too much grease above the piston, the valve unseats and the grease is by-passed back below the piston. It will be noted that the grease which is b .y-passed, that is the grease directly below the piston, is picked up on the next stroke so that no tity of grease is agitated over and over again.

Having described my invention, I claim:

lLfIn a lubricant pumping mechanism, an air motor, a tube extending from said air motor adapted to be submerged in the grease drum, said tube constituting a low pressure cylinder and including;v an inlet, a high pressure cylinder disposed above the air motor, a piston in the low pressure cylinder, a piston in the high pressure cylinder, said pistons attached axially to the piston of the air motor, a. grease supply conduit extending from the low pressure cylinder, by-passing the cylinder of the air motor and communicating with the high pressure cylinder, and a discharge conduit extending from said high pressure cylinder. K

2. In a pumping unit,.a low pressure pump, a high pressure pump disposed above the low pressure pump, a condiit extending from the low pressure pump to the high pressure pump, means operating said pistons of said pumps unitarily in lubricant feeding and discharge strokes whereby high pressure cylinder through the grease, the

specific quangrease within a.`

piston and its cylinder, a tube disposed below said cylinder and adapted to be submergedin the grease within a lubricant drum, said tube constituting a low pressure cylinder, a high pressure cylinder disposed above the power cylinder, a piston in the low pressure cylinder, a piston in the high pressure cylinder, said pistons attached axially to the power piston, a lubricant supply conduit connecting the high pressure cylinder and the low pressure cylinder, a discharge conduit extending from der, and a charging chamber disposed over the high pressure cylinder for containing a supply of lubricant adapted to be drawn into said high pressure cylinder.

4. In a pumping unit, a low pressure pump, a power source, said low pressure pump depending from said power source, a high pressure pump disposed above the power source, and a conduit extending from the low pressure pump to the high pressure pump, the pistons of said pumps fastened unitarily to said power source and adapted to operate in lubricant feed strokes in the same direction whereby the low pressure pump supplies the high pressure pump while the high pressure pump discharges the preceding low pressure strokes. 1

5. A lubricating pump comprising, a high pressure cylinder and piston, a low pressurecylinder and piston, said pistons coaxially disposed,com mon means for reciprocating said pistons said low pressure cylinder disposed downwardly and consisting of an elongated tube having an inlet valve at the base thereof, a charging chamber adjacent and connected to the highpressure cylinder, and a grease ilow conduit between the low pressure cylinder and said chamber.

tons coaxially disposed, said low pressure cylinder disposed downwardly and consisting of an elongated tube having an inlet valve at the base thereof, a grease flow conduit between the low pressure cylinder. and said high pressure cylinder, a charging chamber formed in the grease flow conduit adjacent to and in communication with the high pressure cylinder, and means for bypassing an excess supply of grease from said low pressure pump.

7. In a pump, a high pressure piston in said chamber disposed adjacent tosaid high pressure cylinder, conduit means for supplying` grease to said accumulator chamber, means for maintaining said chamber iilled with grease at all times, said chamber providing an enlarged area adjapressure cylinder, a high of grease adequate for each illling stroke of the trolling the intake of grease to the high pressure cylinder.

the low pressure pump supplies the high pressure pump while the high pressure pump discharges the grease,` and means in said conduit for maintaining a constant supply of lubricant under pressure Pump 3. In a lubricant pumping mechanism, a power for charging said high pressure 'l inder and piston, a low 8. In a lubricating pump, a high pressure cyll pressure cylinder and piston, an air motor cylinder and piston, said pistons disposed coaxially and attached together, a'

.valve operating ring attached to said air motor piston above the cylinder and extending laterally beyond the cylinder, and a toggle valve for controlling the air supply tothe air motor cylinder, said toggle valve actuated by the extension of said ring, said valve xed to the outer wall of the (ylindel',

FRANK c. woman, Jn,- n

said high pressure cylin-v the grease supplied in y cylinder, an accumulator piston and, a valve conl 

